Relationship between bent long bones, bent scapulae, and wavy ribs: malformations or variations?

Area of Science:

• Developmental toxicology
• Teratology
• Skeletal variations

Background:

• Shortened and bent long bones, along with bent scapulae, are occasionally observed in fetuses presenting with wavy ribs.
• Wavy ribs are commonly associated with maternal and developmental toxicity and are considered transient, reversible variations rather than malformations.

Purpose of the Study:

• To review literature on bent long bones and scapulae in the absence of gross limb defects.
• To determine the conditions under which these skeletal changes are reported and their transient or permanent nature.

Main Methods:

• Comprehensive literature search of cited works and subsequent publications.
• Assessment of conditions associated with bent long bones and scapulae.
• Evaluation of the postnatal fate of these skeletal changes.

Main Results:

• Skeletal changes (long bone and/or scapula) occurred less frequently than wavy ribs.
• Maternal and fetal toxicity were observed at identical dose levels in all cases.
• Bent long bones and scapulae were found to be transient, resolving by weaning in some rodent studies.
• Rabbits exhibited fewer skeletal changes at birth compared to rodents, even with severe toxicity.

Conclusions:

• Bent long bones and scapulae are considered secondary to maternal and developmental toxicity.
• These skeletal variations are transient and reversible postnatally.
• Similar to wavy ribs, bent long bones and scapulae should be classified as variations, not malformations.